Variable field mechanism for view finders



Dec. 5, 1944. '0, wrrTEL 2,364,413

VARIABLE FIELD MECHANISM FOR VIEW FINDERS Original Filed July 19, 1941 3 Sheets-Sheet l Dec. 5, 1944. o. wlTTl-:L

VARIABLE FIELD MECHANI-SM FOR VIEW FINDERS 3 Shams-snaaiA 2 Original Filed July 19, 1941 04 //4 ig'. [l2 /2 5 /03 2 .96 v `98 29 l04 [I4 8 4 uw M Otto M'te/ INVENTOR @mf ATTORNEYS Dec. 5, 1944. o. wlTTEL VARIABLE FIELD MECHANISM FOR VIEW FINDERS Original Filed July 19, 1941 5 Sheets-Sheet 5 om Mffe/ INVENTOR A Patented Dec. 5, 1944 Otto Wittel, Rochester, N. Y., assigner to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Griginal application July 19, 1941, Serial No. 403,202. Divided and this application March 31, 1943, Serial No. 481,312

9 Claims.

This invention relates t a. focusing finder system for use with a camera adapted for interchangeable lenses of diterent focal length, and particularly to a variable eld mechanism by means of which the finder eld can be adjusted to correspond to the eld of lenses of different focal length,

This application is` a division of my cepending patent application Serial No. 403,202, led July 19, 1941, now Patent No. 2,341,495, dated February 8, 1944.

One object of the present invention is the provision of a camera. View nder having a novel variable eld mechanism by means of which a field corresponding to lenses of different focal length can be readily obtained.

Another object is to provide a variable eld mechanism which is so designed that a finder housing only slightly larger than the maximum eld of which the device is capable is required to house the mechanism.

And another object is to provide a variable eld mechanism of the type set forth which is simple in construction, efcient in operation and readily adjusted in accordance with lenses of `different focalvlength by the adjustment of a single member movable' over a scale marked in lens focal ler. h:

The novel i amies that I considered characteristic of my i...f'ention are set forth with particularity in the appended claims. The invention itself.` however, both as to its organization and its methods of operation, together with aglditional objects and advantages thereof, will best be understood from the following-description of specic embodiments when read in connection with the accompanying drawings in which` Fig. 1 is a front elevation of a motion picture camera equipped with a focusing finder which is adapted to incorporate a. variable field mechanism constructed in accordance with the present invention, and showing the focusing member for the lens mounted on the camera,

Fig. 2 is a partial front elevation corresponding to Fig. l. and Showing the focusing member removed from the camera,

Fig. 3 is a view corresponding to Figs. 1 and 2, and showing the latch preventing attachment of the focusing member to the camera.

Fig. 4 is a rear elevation of an objective mount includingV a focusing member adapted to be attached to the camera,

Fig. 5 is a rear elevation of including a focusing member adapted to be attached to the camera,

anadapter ring.

Fig. 64 is an enlarged view, partially in section and partially in elevation, showing an objective mount attached to, and locked on, the iront oi the camera,

Fig. 7 is an enlarged sectional view of the adapter, showing the focusing member carried thereby,

Fig. 8 is an enlarged partial side view. of the camera with the cover removed therefrom,

Fig. 9 is a top plan View of the camera, and showing the member and the scale for adjusting the variable eldmechanism constituting the present invention,

Fig. l() is a partial side View of the camera, partially in section, and with the side wall of the finder housing removed to show the position ci, and the manner of mounting, the variable eld mechanism within the finder housing,

Fig. il is an enlarged perspective view of the variable field mechanism constructed in accordance with a preferred embodiment of the present invention,

Fig. l2 is an enlarged section of that portion of Fig. 10 which comprises the variable eld mechanism.

Fig. i3 is a sectional View through the finder showing the method of mounting the variable eld mechanism in the finder housing.

Fig. le is an enlarged sectional view of the upper iront part oi the camera, showing one embodiment of the nder lens mounting and a coupling for adjusting the same,

l5 is a view similar to Fig. 14, but showing s. second embodiment of the finder lens mounting and a coupling for adjusting the same,

Fig. 16 is a diagrammatic View of one form of optical system Which might constitute the camera nder system,

17 is a diagrammatic view of another optical system which might constitute the finder system,

Fig. 13 shows the form of image formed by the finder system shown in Fig. 16, and

Fig. 19 is an enlarged perspective view of the optical dispersing means forming a part of the nder system' shown in Fig. i6.

Like reference characters refer to corresponding parts throughout the drawings.

Briefly, the present invention relates to a focusing nderfor a camera, the nder lens of which is mounted so as to move simultaneously axially of the nder system for focusing and laterally relative to the camera objective for parallax correction. To adapt the finder system for use when camera objectives of dilerent focal included inthe finder housing'by ready adjustment of which the field suitable for camera objectives of different focal lengths can be obtained. Referring now to the drawings, vthe reference numeral 'I0 indicates a motion picture camera of any well-known construction having a. front wall II, a top/wall I2, and a removable side wall or cover I3. The front wall II is provided with an objective socket I4 in alignment with the exposure aperture I5 of the film gate I6, and into which an interchangeable objective mount I1, or objective adapter I8, of the tylpe best shown in Figs. 4 and 5vrespectively and described hereinafter, is adapted to be detachably mounted. As clearly shown in Fig. 2, the front wall of the camera adjacent to the periphery of the objective socket is provided with two diametrically disposed notches I9 adapted to receive two diametrically disposed pins extending laterally from the rear end of the objective mount, or pins 2l extending laterally from the r'ear end of the adapter I8. The notches are disposed at an angle to the vertical,. as shown in Fig.- 2, so that the objective mount, or adapter, must be twisted to the position shown in Fig. 3 in order to attach the mount, or adapter, to the camera, or remove the same therefrom. After the pins on the rear end of the mount are inserted into the notches I9 the 4mount is rotated to an upright position, as shown in Fig. 1, whereupon the pins I9 engage an' arcuate recess 22 Ibehind a front wall of the camera to lock the mount, or adapter, on the camera. This bayonet type lock arrangement for detachably connecting the mount, or adapter, to the camera does not form a part of the present invention per se but is completely disclosed in my U. S. Paten-t 2,110,477, issued March 8, 1938, to which reference can be had for a more detailed description of the same.

On the top wall I2 of the camera is mounted a nder housing which may serve to house a focusing finder system. Referring to Figs. 10, 16, 17, the finder system may comprise a finder lens 26, an optical dispersing arrangement -21, an erector lens 28, a variable field mechanism 29, and an adjustable eyepiece 30. The two finder systems differ only in that the optical dispersing means of the finder system shown in Figs. 10 and 16 comprises a pair of inverted optical wedges 3l and 32 which form a split field of the' type shown in Fig. 18. When the finder lens is not focused on the optical dispersing arrangerment the two parts of the split field will be out of alignment as shown. When the finder lens is moved axially of the optical dispersing means to be in focus thereon then the two parts ofthe split fleld will be in'alignment to indicate that' the finder is in focus. The optical wedges 3| and,32 may be formed by grinding flats in a field lens 33 as shown in Fig. 19. The optical dispersing means 21 may constitute a ground glass 34 intead of the optical wedges as set forth, as shown in Fig. 17, in which case the finder lens 26 is in focus when the image appears sharp on the ground glass as is well known. The optics of the finder system shown in Figs. 10, 16, and 19 is not my invention, but is the invention of Joseph Mihalyi and is disclosed and claimed in patent application Serial No. 478,742, filed March 11, 1943, lby him, now Patent No. 2,341,410, dated February 8, 1941.

. In each of the finder systems disclosed the` finder lens 26 must be moved along the optical axis of the finder system relative to the optical l 2,864,413 `length are used, a variable field mechanism is dispersing means for focusing purposes. In addition, .it is desirable that the finder lens be moved laterally relative to the optical axis of the camera objective during focusing to correct for parallax so that the field viewed in the finder will correspond to that formed by the camera objective in the exposure aperture of the camera. To this end, the lens elements making up the finder lens are confined in a mount which is mounted in the finder housing in such a manner that it simultaneously moves axially of the optical axis of the finder system for focusing purposes and laterally relative to the optical axis of the camera objective for parallax correction, whereby parallax is automatically corrected for during the focusing of the finder.

In the preferred embodiment shown in Figs. 10 and 14 the finder lens is pivotally mounted in the forward end of the finder housing to move through an arc. The pivot point of the finder lens is so located relative to the finder lens that the small arc of movement of the lens required is substantially a straight line at an angle to the optical axis of the finder system whereby the lens is simultaneously moved along the optical axis of the finder system for focusing and laterally of the optical axis -for correction of parallax. The angle of movement of the finder lens will depend upon the lateral spacing of the finder lens and camera objective, because it is this spacing which must be accounted for in the correction of parallax as those skilled in the art are well aware. The nder lens mount includes two rearwardly extending arms 36 on either side of the mount which are pivoted at 31 to the side walls of the finder housing. The finder lens is normally pivoted in a counter-clockwise direction by the action of spring 38, acting on the rear end of the lens mount, and the spring 39 fixed tov the top wall of the finder housing pressing downwardly upon the top of the lens mount. One or more light cushioning springs 40 located on the bottom Wall of the finder housing beneath the lens mount engage the lower part of the lens mount to prevent the same from being forced against the bottom of the nder housing with impact by the action of springs 38 and 39. It is pointed out, however, that the spring, or springsv 40 is not strong enough to overcome the tendency of springs 38 and 39 to move the lens mount in a counter-clockwise direction.

An arm 4I` fixed to the finder lens mount extends from the lower side thereof through van opening 42 in the top Wall I2 of camera I0 and into a recess 43 formed in the upper front portion of the camera directly behind the front wall of the camera, see Fig. 14. The end 44 of this arm engages the nose 45 on the lever, or bellcrank, 46 pivoted atv41 in the recess 43 of the camera. This lever 45 includes an arm 48 the end of which normally extends to a point behind the lens socket and in alignment with a notch I9 in the front wall ofthe camera adjacent said socket where it is adapted to engage a cam or cam follower carried by the camera objective mount or adapter when the same is attached to the camera as will :be fully set forth hereinafter.

In the event the finder housing is so small, or so arranged, that there is not sufficient room available to allow the finder lens to be pivoted on a radius great enough so that the limited arc of movement required will be substantially a straight line, the finder lens may be mounted in the finder housing in such a way as to have a straight line movement at an angle to the optical axis of the nder system. Such a modification of a nder lens' mounting is shown inFlg. whereinl the finder lens mount is shown as having a key and slot connection with the side walls of the nder housing to give the necessary simultaneous axial and lateral movement of the lens for focusing purposes and automatic parallax correction. Referring to Fig. l5, the finder lens mount includes a pair of diametrically disposed keys 50 adapted to engage in slots 5| of the side wall of the housing and which slots are inclined to the optical axis of the finder system as shown. The key and slot connections are shown as being of considerable length in order to prevent the finder lens from tilting during movement, and not to indicate that the lens has this amount of movement. Actually the nder lcns moves only about 1% of an inch axially and e?, of an inch laterally to cover the complete range of focus and parallax correction. 'Ihe lnder lens is normally forced downwardly by a spring 39, as in the embodiment shown in Fig. 14, and is cushioned by a spring. or sp-rings 40 as previously set forth.

' The arm 4l provided in the embodiment shown in Fig. 14 is replaced by a crank 52 pivoted in the camera at 53. one arm 54 of said crank engaging the nose 45 on the lever 46, the other arm 55 of said crank engaging the lower side of the finder lens mount. When the lever 46 is moved counter-clockwise the crank 52 moves clockwise and the arm 55 thereof moves the finder lens upwardly in the slots-5| against the action of the spring 39. The crank 52 is necessary in the coupling shown in Fig. 15, in place of arm 4l of the embodiment shown in Fig. 14, in order that movement of the lever-46 will cause the proper movement of the finder lens and be operatively connected thereto in all positions of the nder lens alone.r its path of movement. In each instance` when the nder lens is moved to its uppermost position in the finder housing it is properly positioned for a focus at innity. As the finder is focused on objects closer than infinity the finder lens automatically moves laterally towards the optical axis of *the camera objective until. when the nder is focused on a subject at approximately two feet. the nder lens is at its lowermost position in the nder housing. The

inclination of the slot 5| in the embodiment shown in Fig'. 13, or the location of the pivot point in the finder lens in the embodiment shown in Fig. 12, are such that the lateral movement of the finder lens accompanying an axial focusing movement thereof insures the finder being autonatically corrected for parallax at any point of focus.

The finder lens is adapted to be moved by adjustment of a focusing member adapted to be detachably mounted in the objective socket on the forward wall of the camera. The focusing member may form a part of the focusing camera objective mount capable of being detachably connected to the camera. or may be carried by an adapter member capable of being detachably connected to the camera to receive interchangeable objective mounts of different focal lengths, all as will be hereinafter fully described.

When sold. the camera is equipped with a focusing obiectve mount of the type best shown ."n Figs. 4 and 6 which is adapted to be detachably connected in the objective socket as previcusly set forth. Only the adjustable parts of the objective mount which are essential to an understanding of the present invention are shown in detail in the drawings, the remaining parts of the mounts, which are well known, being omitted and shown by a general outline. Referring to Figs. 4 and 6, the objective mount includes a rearwardly extending tubular portion 58 which extends well into the recess in the camera whenY the mount is attached thereto by the bayonet lock arrangement previously set forth. The mount also includes a rotatable focusing ring 59 which is threaded to the lens barrel so as to cause aA focusing movement of the lens when rotated.

The rear face of the focusing ring terminates in an axial cam 60 the pitch of which is indicated at 6|. Slidably mounted in a longitudinal slot 62 in the rear tubular portion 58 of the mount is a cam follower 63, one end 64 of which is adapted to engage the face of the axial cam 60 and be moved axially of the mount thereby. The axial slot 52 for the cam follower extends completely to the end of the tubular portion 58 so that the free end of the cam follower is accessible from the end of the mount. Looking at Figs. 2 and 4 it will be noticed that the axial slot S2 and the cam follower 63 are situated to one side of one of the bayonet pins 20 on the mount so that when the mount is rotated to its locked position the end of the cam follower will be in alignment with the arm 48 and the lever 46 in the camera which assumes this position, see Fig. 2. Thus, when the objective mount is placed on the camera the free end of the cam follower is abutted by the arm 48 of the lever 46 and is adapted to be pivoted counterclockwise when the cam follower is moved rearwardly `by adjustment of the focusing ring on the mount. f

The cam follower, which is in effect an actuating member for the finder lens adjusting means 46, is confined against accidental removal from the slot by the diaphragm adjusting ring of the mount, or some equivalent part of the mount. It is moved into, and held in, engagement with the cam by the actionof the springs 38 and 39 normally forcing the finder lens to its lowermost position, said springs tending to move the lever 46 clockwise. Thus the cam follower will act to move the nder lens against the action of the spring when focusing from a close distance toward infinity, and the springs will tend to move the nder lens when focusing is done in the other direction, the cam follower serving merely to limit movement of the lens'under the influence of the springs. The cam on the focusing ring of the objective mount is constructed in accordance with the focal length of the objective so that whenever the finder indicates that a given subject is in focus the camera objective will be focused on said subject.

A person purchasing a camera having a focusing finder of the type set forth might possess one or more interchangeable objectives of different focal length, e. g., telephoto, which would not be equipped with a cam for operating the finder lens adjusting coupling. So that the present camera may be adapted to use all interchangeable cbjectives having no nder lens operating cam of their own the following structure is provided.

Referring to Figs. 5 and '7, an obiective adapter I8 is provided, which adapter may be detachahly mounted in the objective socket I4 in the camera in place of, and in the same manner as, the objective mount supplied with the camera. rl"his adapter. may comprise a rear tubular portion "fl including bayonet pins 2l adapted in engage the notches I9 in the camera front to lock the adapter to the camera in the same manner as the objecvtive mount is attached thereto. The forward end of the tubular portion l terminates in a ange Il against which the rear end of an interchangeadapter it is attached thereto .by the threaded attaching ring 13 rotatably mounted on the forward end of the adapter which threadedly engages threads provided on the rear end of the mount, as is well known.

Rotatably mountedon the adapter is a focusing member 14 the rear bevel face 15 ofwhich includes a focusing scale 16 cooperating with an index 'I1 on a stationary plate 18 forming a part of the adapter, see Fig. 5. The rear tubular pory tion 'lllv of the adapter is provided with a longitudinal slot 19 in which'is sldably mounted a cam follower, or actuating member, 80. The slot 19 and cam follower 80 are located in the same relative position on the adapter as the corresponding parts 62 and 63 are on the objective mount previously described, and serve the same purpose when the adapter is attached to the camera. Instead of the focusing member having an axial cam for moving the cam follower as on the lens mount construction described, there is a threaded connection 6I between the focusing member 'I4 and the cam follower which moves the cam follower axially upon rotation of the focusing member. The pitch of the threaded engagement 8| is equal to the pitch of the cam 60 provided on the lens mount and the focusing scale is the same as that on said lens mount. In order to focus the lens mount carried. by the adapter I8 by use of the focusing nder, the focusing member 14 of the adapter is rotated, while viewing through the finder, until the image appears in focus. 'Ihen the reading of the focusing scale 16 on the focusing member is observed, and the focusing ring of the lens mount is turned to give a corresponding reading on its focusing scale. In other words, the focusing scale 16 on the focusing member is used just to determine a given range and then the focusing ring of the objective mount proper is adjusted to give the focusing range sodetermined.

Referring to Figs. 14 and l5 it will be noted that in most positions of focus less than iniinity the arm 48 on the lever 46 of the camera extends into the axial slot 62 in the end of the mount, or the axial slot 19 in the rear end of the adapter ring 80, depending upon which of the two is attached to the camera. It will be readily appreciated that since this mount, or adapter, must be rotated before it can be removed from the camera, the presence of the arm of this lever in said slot would prevent the removal of the mount. Furthermore, any attempt to rotate the mount or adapter to a position where it could be removed from, or could be attached to, the camera, would tend to bend the arm 48 of the lever 46 if the same were extending into the slot. Therefore, it is essential that means be provided whereby the lever 46 must be pivoted counter-clockwise to a position where the arm 48 thereof will be removed from the slotbefore any rotative movement of the mount. or adapter, necessary to its detachment from the camera can be made.

To this end, l provide a releasable latch mechanism which must positively be actuated before the mount, or adapter, can be rotated relative to the camera, and which latch mechanism is con- J l YM l nected to said lever 46 so as to move the same counter-clockwise to a position where the arm 4l thereof is free of the rear end of the mount, or adapter, when moved to a releasing position. The latch mechanism is also so arranged that it will not permit the return of the lever 46 to its normal position until the mount, or adapter, is in a full attached, or a full released position relative to the camera.

To this end, a latch member is pvoted at 86 in the recess 43 in a camera so that the arm 81 thereof extends through a slot 88 in the front wall of -the camera. This latch member is normally pivoted counter-clockwise by a spring 89 to an operative position wherein it extends into the path of movement of a latch element 90 projecting from a stationary plate 18 fixed to the adapter I8, or from a corresponding plate 18' fixed to the objective mount. It will be apparent from an inspection of Fig. 3 that when the latch member 86 is in its normal operative position it extends into the path of the latch element 90 and prevents the mount, or adapter, from lbeing rotated to a locked position on the mount. It will be obvious from an inspection of Figs. 3 and 14` that when the latch element is manually raised by gripping the ngerpiece 9| thereon the latch element 90 is free to pass thereunder so that the mount or adapter can be rotated relative to the camera. It will also be noticed that the latch element 96 is of such a width that the latch member, once the latch element is moved under it, cannot return to its operative position until the mount, or adapter, is rotated to either its full attached, or its full released, position, It will be evident from an inspection of Figs. l, 6, and l5 that when the mount, or adapter, is rotated to its attached position the latch member drops down behind the right hand edge of the latch element, looking at Fig. 3, so as to positively prevent removal of the mount, or adapter, without first manually raising the latch member.

The latch member 85 includes an arm 92 which is adapted to engage a nger 93 on the lever 46, v

when rotated to an inoperative position, and pivot the lever 46 in a counter-clockwise direction to a point where the arm 48 thereof is removed from the axial slot 62 in the mount, or the axial slot 18 in the adapter, depending upon which member is attached, or is to be attached, to the camera, see Fig. 14. Therefore, before the lens mount, or adapter, can be rotated relative to the camera the latch element must be manually raised and this insures the lever 46 being removed from its operative position so that there is no danger of the same being injured by attachment or removal of the mount or adapter. When the latch member 85 is in its normal operative position, the lever 46 is freed by the latch member and is allowed to return to its cam follower engaging,or operative, position under the action of the springs normally acting on the finder lens to move the same downwardly in the nder housing, see Fig. 15. In Fig. 15 the position the lever 46 assumes when operative is shown by dotted line, and the position it assumes when the latch member 85 is moved to its inoperative position is shown by full line, the position shown being the infinity position.

It is sometimes found necessary to finally adjust the coupling between the nder lens and the focusing member on the camera after the parts are assembled in order to render the mechanism accurate.V To this end the pivot point 41 of the lever 46 is eccentrically mounted` on a screw 56 astucia which ean'ffbe adjusted by a screw driver,jsee Fig- 8. The screw 58 is adapted to'be clamped in any desired position of adjustment by tightening :iown Athe clamping screws 51. It will be readily understood that rotation of screw 50 shifts the pivot point of lever 46 and thereby changes the mechanical advantage of the lever. This adjustment is purely a factory adjustment and is provided only to account for minor inaccuracies in the coupling.

As is well known to vthose skilled in the art the size of the eld covered by different lenses varies in accordance with the focal length of the lens. For instance, a 6-inch telephoto lens will cover a very limited field, whilea 15-mm. lens will cover a much larger field. So that the finder system will indicate the correct size of field covered by the lenses of different focal lengths, according to `the present invention a variable eld mechanism of the type shown in Figs. 10-13 is provided in the finder housing.

This variable field arrangement comprises a -pair of. slotted links 95 pivoted at one end at 96 in overlapping relation on two adjoining walls of the rectangular finder housing. The free end of each of these links is cut down to provide a narrow strip 91 turned at right angles to the links proper to extend transversely of the finder housing and define the size of the field of view. The slot 98 in each link is formed at -an angle to .the

slot of its companion link so that when a pin 99v extending through the slot 98 of each link is moved longitudinally of the finder housing the links of each pair will be moved towards or away from one another depending upon the direction of movement of said pin in accordance with a scale on the top of the finder housing indicating proper setting for different focal length lenses. So that the four framing strips 91 can be adjusted simultaneously through the actuation of a single member, the two pins 9'9 controlling the movement of the links are mounted l on an L-shaped member |0| slidably mounted in the finder housing. This L-shaped member |0| is connected by screws |02 to the under side of a slide |03 slidably monuted ina groove |04 in the outside face of the top of the finder housing, said slide having finger grips |05 extending therefrom to facilitate manual adjustment of the slide. Slide |03 is covered by a plate |06 having an aperture |01 therein through which the individualV readings of the scale |00 of lens focal lengths can be viewed individually as the slide is moved. A spring-pressed ball |09 mounted in a recess I I0 in the side of the groove |04 is adapted to be snapped into and out of notches in the edge of the slide to momentarily arrest the slide in its different positions of adjustment when moved along in the groove. The top of the finder housing is cutA away to provide a recess |I2 in which the finger pieces |05 are adapted to slide Aand be accessible for manual manipulation, see

Figs. 9 and 13. Movement of the slide |03 is lim ited in opposite directions by the engagement of the finger pieces |05 with opposite ends of the recess H2. 'I'he eyepiece 30 of the finder is adapted to bel adjusted longitudinally of the finder system by adjustment of the knob H4 to which the mount for the eyepiece is eccentrically mounted as at H5. This adjustment is provided merely for the purpose of accommodating the finder to the individuals eyesight.

-, The maximum field of the finder system is constantly defined by a fixed frame ||8 attached to *l .the finder housing by a screw adjacent the nar- "'-.row strips 91 constituting the variable field.

When the variable neld arrangement is adJusted for a 15-mm. lens the field will be of its maximum size and the narrow strips 91 will be in alignment with the sides of the fixed frame H0. When the slide |03 is moved rearwardly of the finder housing to give the proper iield for a 3-inch lens, the pins 99 will simultaneously be moved rearwardly and by virtue of their engagement with the slots 98 in the links 05 will cause the free end of the links to move toward the center of the field in a Way to maintain a rectangular field. The fact that the field defining strips 91 are narrow permits the operator to see the maximum field of the nder at all times even though the actual field defined may be much rsmaller than tual eld. The variable field arrangement dis.

closed has the further advantage that the parktioular arrangement of parts requires a finder housing which is only slightly larger than the maximum field to be defined, so that the finder housing can be of a size which fits onto the thinnest of cameras and does not detract from, but adds to, the appearance of the camera.

From the above description of my invention it will be readily appreciated that I have designed a novel variable field mechanism for 'use with a focusing finder of the type set forth which is wholly contained within the finder housing and adapts the finder for use with interchangeable lenses of different focal lengths, and is so constructed that the finder housing need be only slightly larger than the maximum field of the finder system to accommodate the same. The variable field mechanism is rugged in construction and is capable of being adjusted by the operation of a single member conveniently situated on the finder for ready manual operation which is movable over a scale which clearly indicates the several adjustments of field of which it is capable.

While I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except in so far as is necessitated by the scope of the appended claims.

Having thus described my invention, what I claim is new and desire to secure by Letters Patent of the United States is:

1. In a finder having a substantially rectangular casing dening a light conduit, two pairs of relatively narrow and individual field framing members extending in parallel and right angular relation transversely of the light conduit, an arm on each of said framing members extending substantially at right angles -to the framing member with which it is associated and along two adjoining walls of said conduit, means for mounting said arms in said casing whereby each of the framing members is capable of individual movement toward and from the member parallel thereto, means for simultaneously moving each of said members toward or from the center of said conduit to vary the size of the field bounded by said members, said last mentioned means including a member movable longitudinally of the casing and accessible from the outside thereof and including a scale indicating the size of the field bounded by said framing members in terms of the focal length of a lens.

dinally of an adjoining wall of said casing, each of said arms pivoted at one end to the wall of the casing along which it extends, each of said arms provided with a slot inclined relative to the axis of said casing, and the slots of each pair of arms adapted to intersect at a given point, a

, framing member on the Afree end of` each of said of the conduit, means for simultaneously pivoting y each of said members toward and from the center of said conduit to vary the size of the field bounded by said frame members, said means including a member accessible from the outside of said casing and movable longitudinally therel 3. In a nnder having a substantially rectangular casing defining a light conduit, two pairs of relatively narrow iield framing members extending in parallel and right angular relation transversely of the light conduit, arms on each of said framing members extending substantially at right angles to the framing members with which it is associated and along two adjoining walls of said conduit, said arms individually pivoted in pairs to two adjoining walls of said casing whereby the ends thereof to which the framing members are attached may swing toward and from the center of the conduit, means for simultaneously pivoting each of said members toward and from the center of said conduit to vary the size of the eld bounded by said frame members, said means including a plurality of movable pins engaging slots in each of said arms, and means accessible from the outside of the casing for simultaneously moving said pins longitudinal of said casing by the same amount.

4. In a finder having a substantially rectangular casing defining a light conduit, two pairs of relatively narrow field framing members extending in parallel and right angular relation transversely of the light conduit, arms on each of said framing members extending substantially at right angles to the framing members with which it isassociated and along two adjoining walls of said conduit, said arms individually pivoted in pairs to two adjoining walls of said casing whereby the ends thereof to which the framing members are attached may swing toward and from the center of the conduit, means for simultaneously pivoting each of said members toward and from the center of said conduit to vary the size of the eld bounded by said frame members, said means including an angle member mounted in said casing with the two arms thereof parallel to and extending transversely of the two adjoining walls of the casing along which said arms of the framing members extend and adapted to slide longitudinally of said casing, a pin extending from each arm of said angle member, each pin extending into engagement with a slot in each pair of arms and inclined to the path of movement of said pin, and a member accessible from the outside of the finder casing for moving said angle member longitudinally of said casing, said last mentioned member including a scale indicating the size of the field bounded by said framing members in terms of the focal length of a lens.

5. In a finder having a substantially rectangular casing defining a light conduit, a pair of arms extending longitudinally of one wall of said casyarms at right angles to the arms and extending in parallel and right angular relation transversely of the light conduit, a pair of pins, one extending through each slot of the two pairs of arms and movable longitudinally of the casing to cause `the arms of each pair to simultaneously pivot toward or away `from one another,and means accessible from the outside of the casing for moving said two pins simultaneously longitudinally of said casing.

6. In a finder having a substantially rectanllf lar casing dening a light conduit, a pair of arms extending longitudinally of one wall of said casing, a second pair of arms extending longitudinally of an adjoining wall of said casing, each of said arms pivoted at one end to the wall of the casing along which it extends, each of said arms provided with a slot inclined relative to the axis of said casing. and the slots of each pair of arms adapted to intersect at a given point, a framing member on the free end of each of said arms at right angles to the arms and extending lin parallel and right angular relation transversely of the light conduit, a right angle member slidably mounted in one corner of said casing to move longitudinally thereof and with one branch thereof extending in overlapping relation transversely of each of said pair of arms, a pin extending from each` branch of said right angle member and into engagement with each of said slots in each pair of arms, and means accessible from the` outside of said casing for shifting said right angle member longitudinally of said casing to swing each of said framing members simultaneously toward and from the center of the conduit to vary the eld bounded thereby, said last mentioned means including a scale for indicating the size of the field formed by said members in terms of the focal length of a lens.

'7. In a finder having a substantially rectangular casing defining a light conduit, a pair of arms extending longitudinally of one wall of said casing, a second pair of arms extending longitudinally of an adjoining wall of said casing, each of said arms pivoted at one end to the wall of the casing along which it extends, each of said arms provided with a slot inclined relative to the axis of said casing, and the slots of each pair of arms adapted to intersect at a given point, a framing member on the free end of each of said arms at right angles to the arms and extending in parallel and right angular relation transversely of the light conduit, a right angle member slida'bly mounted in one corner of said casing to move longitudinally thereof and with one branch thereof extending in overlapping relation transversely of each of said pair of arms, a pin extending from each branch of said right angle right angle member to move the same, said slide provided with a scale for indicating the size of the field bounded by said field members in terms ingga second pair of arms extending longituof the focal length of a-lens, finger piecesv on said slide and extending from said groove to be readily accessi-ble for manually moving the slide, and a cover plate over said groove and slide provided with an aperture through which only the pertinent scale reading is visible at any one time.

8. In a iinder having a substantially rectangular casing defining a li-ght conduit, a pair of arms extending longitudinally of one wall of said casing, a second pair of arms extending longitudinally of an adjoining wall o-f said casing, each of said arms pivoted at one end to the wall of lthe casing along which it extends, each of said arms providedwith a slot inclined relative to the -axis of said casing, and the slots of each pair of arms adapted to intersect at a given point, a framing member on the free end of each of said arms at right angles to the arms and extending in parallel and right angular relation transversely of the light conduit, a right angle member slidably mounted in one corne-r of said casing to move longitudinally thereof and with one branch thereof extending in overlapping relation transversely of each of said pair of arms, a pin extending from each branch of said right angle member and into engagement with each of said slots in each pair of arms, a slide movable longitudinally of the `casing in a groove provided in the outside wall thereof and connected to said right angle member to move the same, said slide provided with a scale for lindicating the size of the eld bounded by said field4 members in terms of the focal length of a lens, nger pieces on said slide and extending from said groove to be readily accessible for manually moving the slide, a cover plate over said groove and slide provided with an aperture through which only the pertinent scale reading is -visible at any one time, and means for temporarily restraining movement of said slide when the eld is adjusted in accordance with a given focal length lens for the purpose of indicating to the operator when the mechanism is properly adjusted.

9. In a. iinder having a substantially rectangular casing dening a light conduit, a pair of arms extending longitudinally of one wall of said casing, a second pair of arms extending longitudinally of an adjoining wall of said casing, each of said arms pivoted at one end to the wall of the casing along which it extends, each of said arms provided with a slot inclined rel'- ative tothe axis of said casing, and the slots of each pair of arms adapted to intersect at a given point, a framing member on the free end of each of said arms at right angles to the arms and extending in parallel and right angular relation transversely of the light conduit, a right angle member slidably mounted in one corner of said casing to move longitudinally thereof and with one branch thereof extending in overlapping relation transversely of each of said pair of arms, a pin extending from each fbranch of said right angle member and into engagement with each of said slots in each pair of arms, a. slide movable longitudinally of the casing in a groove provided in the outside wall thereof and connected to said right angle member to move the same, said slide provided with a scale for indicating the size of the eld bounded by said eld members in terms of the focal length of a lens, finger pieces on said slide and extending from said .groove to be readily accessible for manually moving the slide, a cover plate over said groove and slide provided with an aperture through which only the pertinent scale reading is visible at any one time, a plurality of notches spaced longitudinally along one edge of said slide in accordance with the spacing of the different scale readings, and a spring pressed -member normally engaging the side of said slide and adapted to snap into said notches to indicate when the mechanism is properly adjusted to one of its several given positions of adjustment.

OTTO WI'I'I'EL. 

